Greater L.A. to heat up an average 4 to 5 degrees by mid-century

and when you tack on warming of 5 to 6 degrees, that’s a pretty noticeable difference,” Hall said. “If humans are noticing it, so are plants, animals and ecosystems. These places will be qualitatively different than they are now.”

The most sophisticated regional climate study ever developed
The type of climate modeling used in the study is done almost exclusively at the national or international level, said Paul Bunje, the managing director of the LARC, which is based at UCLA’s Institute of the Environment and Sustainability. Other cities and states have localized global climate models — but usually by localizing only one model. Hall’s team needed months of computer time to downscale twenty-two global climate models, each with slightly different assumptions about how to predict climate change or factors like future greenhouse gas emissions.

Hall’s team included UCLA postdoctoral students Fengpeng Sun and Daniel Walton and graduate student Mark Nakamura. Once they recalculated the almost two dozen global models at the local level, the team analyzed the results and integrated them into an ensemble projection to create the forecast for the entire region.

“This is the best, most sophisticated climate science ever done for a city,” said Bunje, who is also the executive director of UCLA’s IoES Center for Climate Change Solutions.

“L.A. is one of the first cities to get its act together, from the scientists all the way up to the mayor,” Bunje said. “Nobody knew precisely how to adapt to climate change because no one had the data — until now. These are shocking numbers, and we will have to adapt.”

Cutting emissions will reduce but not eliminate warming
Cutting greenhouse gas emissions could reduce the impact on Los Angeles, Hall said. Even if the world has unanticipated — and perhaps unrealistic — success in drastically reducing greenhouse gas emissions, the greater Los Angeles area will still warm to about 70 percent of the currently predicted levels, the study found.

“We looked not only at a business-as-usual scenario where greenhouse gas emissions continue but also at a scenario where emissions are curtailed,” Hall said. “Even if we drastically cut pollution worldwide, there will still be quite a bit of warming in Los Angeles. I was a little taken aback by how much warming remains, no matter how aggressively we cut back. It was sobering.”

“Mid-Century Warming in the Los Angeles Region” is the first of five planned studies Hall will conduct for the city and the LARC about how climate change will affect the Southland. Hall’s team plans to develop similarly comprehensive models for local rainfall, Santa Ana wind patterns, coastal fog (including June gloom), and soil moisture, run-off and evaporation. Preliminary results already show that Santa Ana winds and June gloom will react to climate change, Hall said.

Global warming is local warming
“I think for many people, climate change still feels like a nebulous, abstract, potential future change, and this makes it more real,” Hall said. “It’s eye-opening to see how much it will warm where you live. This data lays a foundation for really confronting this issue, and I’m very optimistic that we can confront and adapt to a changing climate.”